In recent years, many tea-based beverages packaged in cans, PET bottles or the like have been put on the market. These beverages are meant to be thirst-relieving beverages, but also have an aspect of favorite beverages, as compared with beverages prepared by users themselves from tea leaves. The beverages packaged in cans, PET bottles or the like are often very convenient in a sense that they can be readily consumed at any time because they are sterilized beforehand and can be stored over a long term. On the other hand, these packaged beverages are subject to some limitations arisen from their production process, and their taste sensation does not necessarily satisfy consumers' demand.
With respect to beverages with the distinct flavor and taste of green tea such as green tea beverages, there are two directions in designing their flavor and taste: one is beverages with a directionality of enriching catechins, increasing bitterness and hence providing “refreshment”, and the other is those with a directionality of inhibiting the dissolution of catechins, reducing bitterness and hence placing an importance on “deliciousness”.
In beverages weighing in deliciousness, a “refined taste” inherent in teas extracted at home is not generated sufficiently, because the extract needs to become a relatively dilute composition in order to avoid a smell of heat sterilization. The term “refined taste” used herein is one of the general expressions that describe tastes of green tea, and components that make up a refined taste include amino acids, catechins, purine bases, saccharides, organic acids, minerals, and soon. Such a refined taste is considered to have a relation to the harmony of these components, and among these, amino acids and catechins are considered to have a central role [“Chori Kagaku (Cookery Science)”, 25(1), 55, 1992].
Research has been done to develop means that prevent generation of above-described smell of heat sterilization. Those reported include a process which comprises extracting tea leaves with cold water of 20° C. or lower, removing the thus-obtained extract, and then producing a beverage from the tea leaves left as an extraction residue (JP-A-11-113491) and a process which comprises producing a beverage from a residue of tea leaves that has been once subjected to extraction (JP-A-2001-231450).
However, amino acids and the like, which are components associated with the refined taste, are considered to be extractable with tepid water. The above-described processes have both resolved the problem of the generation of a smell of heat sterilization by eliminating portions of the components, which are associated with the refined taste of green tea, by the first extraction. As a result, these processes enable the production of highly-refreshing, tea-based beverages enhanced in bitterness but not beverages having a flavor close to home-made tea excellent in refined taste.
Further, JP-A-2000-50799 discloses an extraction process to obtain a tea having deliciousness and reduced bitterness; namely, tea leaves are immersed in still water maintained at 0 to 36° C. from which dissolved oxygen has been eliminated, and the resulting extract is filtrated. It also discloses a process by which water maintained at 0 to 36° C., from which dissolved oxygen has been eliminated, is constantly supplied into the still water. These processes, however, require an operation for the elimination of dissolved oxygen from water as well as equipment for constantly supplying such water, and therefore, cannot be adopted industrially.
On the other hand, catechins contained in tea are known to have a suppressing effect on an increase in cholesterol level (JP-B-1620943), an inhibitory effect on α-amylase activity (JP-B-3018013), and the like. To obtain such physiological effects of catechins by drinking tea, it is necessary for an adult to drink tea as much as from 4 to 5 cups in a day [“SHOKUHIN KOGYO (THE FOOD INDUSTRY)”, 35(14), 26-30, 1992]. Therefore, a demand has been existed to develop a beverage containing higher concentration of catechins that enables one to take a large amount of catechins in a simpler and easier way.
To add catechins as an active ingredient at high concentration, two methods were contrived. One of these methods is to add pulverized tea leaves (JP-A-10-234301). This method, however, has drawbacks resulting from the addition of tea dust at high concentration, such as an uncomfortable powdery feeling, no good feeling in the throat and a poor aftertaste. Furthermore, in the case of a beverage supplied after its production by way of its distribution, pulverized tea leaves as an active ingredient tend to be precipitated in the bottom of the beverage or are sometimes afloat on the surface of the beverage. In the case of a beverage in a transparent container such as a PET bottle, such a precipitate significantly impairs the commercial value due to its external appearance. The formation of a precipitation may be acceptable in a beverage intended for physiological effects, but operations such as shaking or agitating the beverage become necessary to evenly disperse the pulverized tea leaves upon drinking.
The other method is to add a concentrated tea extract or a concentrate of a commercial tea extract or a purified product thereof (hereinafter referred to as “a catechin preparation”), so that the concentration of catechins in dissolved state increases. When a concentrated tea extract or an unpurified catechin preparation is used, an uncomfortable feeling that could be caused by tea dust or the like upon drinking can be reduced. However, because of an unpleasant smell produced upon its heat sterilization, and the bitterness and astringency of catechins dissolved therein, a beverage with a catechin preparation added abundantly therein becomes excessively unpleasant in its smell and bitter and astringent in its taste. To bring about the physiological effects of catechins, it is necessary to make a beverage suitable for long-term storage or everyday drinking. Nonetheless, the beverages obtained by these means are unable to meet this requirement.
As a method for reducing the generation of an unpleasant smell caused by heat processing, a couple of techniques have been disclosed. JP-A-2001-231450, for example, discloses a process for the production of a canned green tea beverage making use of a green tea extract of the second or subsequent brew from which components with an unpleasant smell are eliminated. The primary purpose of this method is directed at the extraction of catechins from an extract and the reduction of a smell of heat sterilization, so there has been a limitation arising from the defect that the components of the first brew cannot be used. In addition, this process provides no solution to the problem of such excessive bitterness and astringency as in high catechin beverages.
JP-A-11-113491, on the other hand, discloses a technique for reducing a smell of heat sterilization in a production process of a tea beverage such as sencha (middle-grade green tea) or oolong tea. This technique comprises extracting tea leaves with cold water of 20° C. or lower, removing the resultant cold water extract, and then re-extracting the residue with warm water of from 30 to 95° C. However, the problem that the components of the first brew cannot be used has not been solved either in this technique, and also the same problems stated above remain unsolved. In addition, the conditions for the cold water extraction in the first brew are not adequate, thereby raising another problem in that the production of a “coarse taste” in the second brew cannot be inhibited.
Because the components of the first brew cannot be used in these two prior art techniques, there is also a problem that the resulting beverage is a beverage free of so-called delicious components such as amino acids, saccharides and organic acids.
The present invention provides a production process of a green tea flavor for obtaining more authentic packaged tea-based beverages with an importance placed on deliciousness, and a beverage making use of the green tea flavor and reduced in an unpleasant smell and coarse taste while maintaining a refined, strong taste.
The present invention also provides a production process of a dried green tea polyphenol, which can reduce a green-tea-derived unpleasant smell and coarse taste generated upon heat sterilization subsequent to its addition to a beverage albeit a polyphenol derived from green tea, and a production process of a beverage, which makes use of the dried green tea polyphenol.
Further, the present invention provides a beverage which, even when it contains catechins at high concentration, emits no unpleasant smell but retains its original flavor and aroma derived from a green tea extract upon sterilization.
Yet further, the present invention provides an efficient production process of a green tea beverage, which contains catechins at high concentration and is reduced in “the production of an unpleasant smell” upon heat sterilization as well as in “coarse taste”, and a green tea beverage obtained as described above.